JP2022184314A - Imaging element and imaging device - Google Patents

Abstract

To provide an imaging element with which it is possible to suppress an increase in chip area.SOLUTION: The imaging element comprises: a first photoelectric conversion unit for generating electric charges by photoelectric conversion; a second photoelectric conversion unit for generating electric charges by photoelectric conversion; a first signal line in which a first signal based on electric charges generated by the first photoelectric conversion unit is outputted; a second signal line in which a second signal based on electric charges generated by the second photoelectric conversion unit is outputted; a first comparison unit for comparing the signal outputted to the first signal line with a reference signal; a second comparison unit for comparing the signal outputted to the second signal line with a reference signal; and a control unit for exercising first control for causing the first signal to be outputted to the first signal line and the second signal to be outputted to the second signal line and second control for causing the first signal to be outputted to the first and second signal lines.SELECTED DRAWING: Figure 4

Description

The present invention relates to an imaging device and an imaging device.

An imaging device having an image sensor circuit and a correlated double sampling circuit is known (Patent Document 1). Conventionally, there has been a demand for reduction in circuit area.

WO2008/129885

According to the first aspect, the imaging device includes a first photoelectric conversion unit that generates electric charge by photoelectric conversion, a second photoelectric conversion unit that generates electric charge by photoelectric conversion, and the electric charge generated by the first photoelectric conversion unit. a first signal line for outputting a first signal based on, a second signal line for outputting a second signal based on the charge generated by the second photoelectric conversion unit, and output to the first signal line a first comparison unit that compares the signal and the reference signal; a second comparison unit that compares the signal output to the second signal line and the reference signal; and outputting the first signal to the first signal line. and a control unit that performs first control for outputting the second signal to the second signal line and second control for outputting the first signal to the first signal line and the second signal line. .
According to a second aspect, an imaging device includes the imaging device according to the first aspect, and a generator that generates image data based on a signal output from the imaging device.

It is a figure which shows the structural example of the imaging device which concerns on embodiment. 1 is a block diagram showing a configuration example of an imaging device according to an embodiment; FIG. 3A and 3B are diagrams illustrating configuration examples of pixels of an image sensor according to the embodiment; FIG. It is a figure which shows the example of a structure of a part of image pick-up element which concerns on embodiment. FIG. 5 is a diagram for explaining an example of readout control by the imaging element according to the embodiment; FIG. 10 is a diagram for explaining another example of readout control by the imaging device according to the embodiment; 4 is a timing chart for explaining an example of readout control by the imaging element according to the embodiment; FIG. 10 is a diagram for explaining a configuration example of part of an imaging device according to Modification 1; FIG. 11 is a diagram for explaining a configuration example of part of an imaging device according to modification 2;

(Embodiment)
FIG. 1 is a diagram showing a configuration example of a camera 1, which is an example of an imaging device according to an embodiment. The camera 1 includes a photographing optical system (imaging optical system) 2 , an imaging device 3 , a control section 4 , a memory 5 , a display section 6 and an operation section 7 . The photographing optical system 2 has a plurality of lenses including a focus lens (focusing lens) and a diaphragm (aperture diaphragm), and forms a subject image on the imaging device 3 . Note that the photographing optical system 2 may be detachable from the camera 1 .

The imaging element 3 is an imaging element such as a CMOS image sensor or a CCD image sensor. The imaging device 3 receives the light flux that has passed through the imaging optical system 2 and captures the subject image formed by the imaging optical system 2 . The imaging element 3 is provided with a plurality of pixels each having a photoelectric conversion unit two-dimensionally (row direction and column direction). The photoelectric conversion unit is composed of a photodiode (PD) and converts incident light into charges. The imaging device 3 photoelectrically converts the received light to generate a signal, and outputs the generated signal to the control unit 4 .

The memory 5 is configured by a nonvolatile storage medium or the like. The memory 5 stores image data, programs and data used for controlling each part of the camera 1, and the like. The control unit 4 writes data to the memory 5 and reads data from the memory 5 .

The display unit 6 is a liquid crystal display, an organic EL display, or the like. The display unit 6 displays a through image (live view image) of the subject, an image based on the image data stored in the memory 5, an image showing the focus detection area (AF area) such as an AF frame, shutter speed, aperture value, and the like. Displays information about and menu screens. The display unit 6 may include a touch panel and function as an input/output unit. The display unit (input/output unit) 6 may generate a signal based on the user's operation and output it to the control unit 4 .

The operation unit 7 includes members such as a release button, a power button (switch), operation buttons, and switches for switching various modes, and receives operations for the camera 1 . The operation unit 7 detects a user's operation and outputs a signal based on the operation to the control unit 4 . Note that the operation unit 7 may include the touch panel of the display unit 6 .

The control section 4 has a processor and memory, and controls each section of the camera 1 . The control unit 4 has devices such as CPU, GPU, FPGA, and ASIC, and memories such as ROM and RAM. The control unit 4 reads and executes a program stored in the memory. The control unit 4 can also be said to be a processing unit (information processing unit) that performs information processing based on a program.

The control unit 4 supplies signals for controlling the image sensor 3 to the image sensor 3 and controls the operation of the image sensor 3 . The control unit 4 causes the image pickup device 3 to pick up a subject image and output pixel signals when performing still image shooting, moving image shooting, displaying a through image of the subject on the display unit 6, or the like. . The control unit 4 performs various image processing on the signal of each pixel output from the image sensor 3 to generate image data including the signal of each pixel. The control unit 4 is also a generation unit 4 that generates image data, and generates still image data and moving image data based on signals output from the imaging device 3 . The control unit 4 performs image processing such as color interpolation processing and gradation conversion processing.

FIG. 2 is a block diagram showing a configuration example of an imaging device according to the embodiment. The imaging device 3 is configured by laminating a first substrate 111 on which a plurality of pixels 10 are formed and a second substrate 112 on which a plurality of analog/digital converters (AD converters) 60 are formed. The first substrate 111 and the second substrate 112 are each configured using a semiconductor substrate. The circuits provided on the first substrate 111 and the circuits provided on the second substrate 112 are electrically connected by connecting portions such as electrodes and bumps.

The first substrate 111 has a plurality of regions 20 in which a plurality of pixels 10 are respectively arranged. In the example shown in FIG. 2, six regions 20 are illustrated. Each of these six regions 20 indicates one region when the region in which the pixels 10 are arranged on the first substrate 111 is divided into regions each including a predetermined number of pixels. In addition, each area|region 20 may overlap partially, and does not need to overlap. The number of pixels in each region 20 may be 4 pixels (2 pixels×2 pixels) or 16 pixels (4 pixels×4 pixels), or may be an arbitrary number. The regions 20 are hereinafter referred to as pixel blocks 20 .

The pixels 10 output photoelectric conversion signals and dark signals, which will be described later, to the second substrate 112 . A signal line 30 is a signal line that connects the pixel 10 and the AD converter 60 , and a signal is output from the pixel 10 . The signal line 30 is a signal line using connection portions such as electrodes and bumps. A current source 35 and an AD converter 60 are provided for each of the plurality of signal lines 30 .

The second substrate 112 has a current source 35 , an AD conversion section 60 , a read control section 80 and a signal processing section 100 . In the imaging device 3 , a signal line 30 , a current source 35 and an AD converter 60 are provided for each pixel block 20 . A current source 35 is connected to each pixel 10 of the pixel block 20 via a signal line 30 . The current source 35 generates a current for reading out signals from the pixels 10 and supplies the generated current to the signal line 30 and each pixel 10 of the pixel block 20 .

The read control unit 80 is composed of a plurality of circuits such as a timing generator, logic circuits (AND circuit, OR circuit, etc.), latch circuits, buffers, and the like. The readout control unit 80 is controlled by the control unit 4 of the camera 1, supplies signals such as a signal TX, a signal RST, and a signal SEL, which will be described later, to each pixel to control the operation of each pixel. The readout control unit 80 supplies a signal to the gate of each transistor of the pixel to turn the transistor on (connected state, conductive state, short-circuited state) or off state (disconnected state, non-conductive state, open state, cutoff state). and The read control unit 80 may be arranged separately on the first substrate 111 and the second substrate 112, or may be arranged on different substrates than the first substrate 111 and the second substrate 112. FIG.

The AD conversion section 60 is configured including a comparison section and a storage section, which will be described later. The AD converter 60 converts the pixel signal (photoelectric conversion signal, dark signal), which is an analog signal input from each pixel 10 of the pixel block 20 via the signal line 30, into a digital signal of a predetermined number of bits. . The pixel signals converted into digital signals are output to the signal processing unit 100 .

The signal processing unit 100 is composed of a plurality of circuits such as a logic circuit, a memory circuit, and an output circuit compatible with a high-speed interface. The signal processing unit 100 performs signal processing, such as correlated double sampling for performing difference processing between a dark signal and a photoelectric conversion signal, and processing for correcting the amount of signal, on the input pixel signal. The signal processing unit 100 outputs the processed signal to the control unit 4 of the camera 1 .

The imaging device 3 is also provided with a switch SW1 (switches SW1a to SW1e in FIG. 2) for electrically connecting or disconnecting the signal line 30 and another signal line 30 other than the signal line 30. FIG. The switch SW1 is composed of a transistor. The switch SW1 is the connection section 1 and connects two adjacent signal lines 30 . The read control unit 80 supplies a signal to each of the switches SW1a to SW1e to control on/off of each switch. It can also be said that the switch SW1 (connection unit 1) is a switching unit that switches between connection and disconnection.

The image pickup device 3 according to the present embodiment can perform a process (first readout control) of reading signals of the pixels of the pixel block 20 to the AD conversion unit 60 provided for the pixel block 20 and AD converting them. . The imaging device 3 can also perform a process (second readout control) of AD-converting the pixel signals by controlling the switch SW1 to read them out to the plurality of AD converters 60 . The control unit 4 of the camera 1 controls the imaging element 3 to select (set) a method of processing the pixel signal.

In the second readout control, pixel signals are input to a plurality of AD converters 60 and converted into digital signals by the plurality of AD converters 60 . A pixel signal converted into a digital signal by each of the AD converters 60 is output to the signal processor 100 . The signal processing unit 100 performs a process of averaging pixel signals converted into a plurality of digital signals. The imaging device 3 can implement correlated multi sampling (CMS) in which one pixel signal is AD-converted by a plurality of AD converters 60 and then averaged. The imaging device 3 performs second readout control when reading out signals from some pixels by thinning out specific pixels out of all the pixels 10, or when adding (mixing) and reading out signals of a plurality of pixels. . The signal processing unit 100 performs signal processing such as CMS processing on the input pixel signal, and outputs the signal of each pixel after the signal processing to the control unit 4 .

FIG. 3 is a diagram illustrating a configuration example of a pixel of an imaging device according to the embodiment; The pixel 10 has a photoelectric conversion unit 11 , a transfer unit 12 , a floating diffusion (FD) 13 , a reset unit 14 , an amplification unit 15 and a selection unit 16 . The photoelectric conversion unit 11 is a photodiode PD that converts incident light into charges and accumulates the photoelectrically converted charges.

The transfer unit 12 is composed of a transistor M1 controlled by a signal TX, and electrically connects or disconnects the photoelectric conversion unit 11 and the FD 13 . The transfer unit 12 transfers the charge photoelectrically converted by the photoelectric conversion unit 11 to the FD 13 . Transistor M1 is a transfer transistor. The FD 13 accumulates (holds) the charges transferred to the FD 13 . The FD 13 is the accumulation unit 13 and accumulates charges generated by the photoelectric conversion unit 11 .

The amplifying unit 15 is composed of a transistor M3 whose gate (terminal) is connected to the FD13. The amplification unit 15 amplifies and outputs a signal based on the charges accumulated in the FD 13 . A drain (terminal) of the transistor M3 is connected to a power supply line (power supply voltage VDD). A source (terminal) of the transistor M3 is connected to the signal line 30 via the selection section 16 . Transistor M3 is an amplification transistor. The amplification unit 15 and the selection unit 16 can also be said to be an output unit that generates and outputs a signal based on the charges generated by the photoelectric conversion unit 11 .

The reset unit 14 is composed of a transistor M2 controlled by a signal RST, and resets the charge accumulated by the FD13. A reset unit (discharge unit) 14 discharges the charge accumulated in the FD 13 and resets the voltage of the FD 13 to a reset voltage (voltage corresponding to the voltage VDD). Transistor M2 is a reset transistor.

The selection unit 16 is composed of a transistor M4 controlled by a signal SEL, and electrically connects or disconnects the amplification unit 15 and the signal line 30 . The transistor M4 of the selection unit 16 outputs the signal from the amplification unit 16 to the signal line 30 when it is on. Transistor M4 is a select transistor.

The pixel 10 transmits to the signal line 30 a signal (dark signal) when the voltage of the FD 13 is reset and a signal (photoelectric conversion signal) corresponding to the charge transferred from the photoelectric conversion unit 11 to the FD 13 by the transfer unit 12. Output sequentially. The photoelectric conversion signal is an analog signal generated based on charges photoelectrically converted by the photoelectric conversion unit 11 . The dark signal becomes an analog signal indicating a reference level for the photoelectric conversion signal, and is used for correction of the photoelectric conversion signal. A dark signal can also be said to be a signal used for removing noise contained in a photoelectric conversion signal.

The readout control unit 80 (see FIG. 2) controls the signal TX, the signal RST, the signal SEL, etc. input to each pixel 10 to read out the dark signal and the photoelectric conversion signal. Dark signals and photoelectric conversion signals sequentially output from the pixels 10 are input to the AD converter 60 via the signal line 30 and converted into digital signals.

FIG. 4 is a diagram illustrating a configuration example of part of an imaging device according to the embodiment. The imaging device 3 has a pixel block 20 , a supply section 40 , an AD conversion section 60 and a signal processing section 100 . 4, one pixel 10 (referred to as pixel 10a) in pixel block 20a of the plurality of pixel blocks 20 provided in image sensor 3 and one pixel 10 (referred to as pixel 10b) in pixel block 20b are shown. ) are shown.

A ramp signal Vramp, which is a signal whose signal level changes over time, is input to the supply unit 40 from a signal generation unit (signal generation circuit) (not shown) through the signal line 38 . The supply unit 40 is controlled by the read control unit 80 (see FIG. 2), generates the signal Vin based on the signal Vramp, and supplies the signal to the AD conversion unit 60 . The signal Vin is a signal whose signal level changes with the lapse of time, and serves as a reference signal used by the comparison unit 50 of the AD conversion unit 60 for comparison with pixel signals. Note that the supply unit 40 may be included in the AD conversion unit 60 .

In the example shown in FIG. 4, the supply unit 40 includes a first capacitor 41, a plurality of second capacitors 42 (second capacitors 42a to 42d), a plurality of switches SW2a and SW2b (switches SW2a1 to SW2a4, switches SW2b1 to SW2b4). ) and The first capacitor 41 and the second capacitors 42a to 42d each have a capacitance value of C, for example. The supply unit 40a generates the reference signal Vin1 and outputs it to the AD conversion unit 60a. The supply unit 40b generates the reference signal Vin2 and outputs it to the AD conversion unit 60b.

The first capacitor 41 is connected between the signal line 38 and the AD converter 60 . A ramp signal Vramp whose signal level changes over time is input to one terminal (electrode) of the first capacitor 41 via the signal line 38 . The other terminal of the first capacitor 41 is electrically connected to the plurality of second capacitors 42 and the AD converter 60 via the signal line 48 .

The second capacitor 42 is a capacitor electrically connected to the first capacitor 41 . One terminal of the second capacitor 42 is electrically connected to the first capacitor 41 and the AD converter 60 . The other terminal of the second capacitor 42 is connected to the signal line 39 via the switch SW2a, and is connected to the ground line via the switch SW2b. The signal line 39 is supplied with a signal Voffset having a predetermined voltage (for example, a power supply voltage or a ground voltage) from a signal generator (not shown).

The switch SW2a is the connecting portion 2a, and electrically connects or disconnects the second capacitor 42 and the signal line 39 to which the signal Voffset is input. The switch SW2b is the connecting portion 2b and electrically connects or disconnects the second capacitor 42 and the ground line to which the ground voltage is applied. The switch SW2a and the switch SW2b are composed of transistors. The switches SW2a and SW2b (connection units 2a and 2b) can also be said to be switching units for switching between connection and disconnection. The read control unit 80 supplies a signal to each of the switches SW2a1 to SW2a4 and the switches SW2b1 to SW2b4 to turn on/off each switch.

The magnitude of the reference signal Vin output to the signal line 48 changes depending on the connection state of the second capacitor 42 connected to the first capacitor 41 . By controlling each switch of the supply unit 40, the read control unit 80 can set (change) the connection destinations of the second capacitors 42a to 42d and adjust the voltage of the reference signal Vin. The supply unit 40 is controlled by the readout control unit 80 to change the signal level of the reference signal Vin supplied to the AD conversion unit 60 . The supply unit 40 can also be said to be an adjustment unit that adjusts the signal level of the reference signal Vin.

The AD conversion unit 60 has a comparison unit 50 and a storage unit 55, and converts pixel signals input via the signal line 30 into digital signals. The comparison unit 50 is configured including a comparator circuit. A pixel signal (photoelectric conversion signal, dark signal) is input from the pixel 10 to the first terminal 51 of the comparison unit 50 via the signal line 30 . The second terminal 52 of the comparing section 50 is supplied with the reference signal Vin whose signal level changes over time from the supplying section 40 via the signal line 48 . The comparison unit 50 compares the signal input from the pixel 10 with the signal Vin, and outputs an output signal, which is the comparison result, from the output terminal 53 .

The storage unit 55 is composed of a plurality of latch circuits corresponding to the number of bits of the digital signal to be stored. The storage unit 55 receives an output signal indicating the comparison result from the comparison unit 50 and receives a digital signal based on the count result from a counting unit (counter circuit) (not shown). Based on the output signal of the comparison unit 50 and the output signal of the count unit, the storage unit 55 converts a digital signal indicating a count value corresponding to the elapsed time from the start of comparison by the comparison unit 50 until the comparison result is inverted. It is stored as the signal of the subsequent pixel. In the example shown in FIG. 4 , the storage unit 55 stores data until the magnitude relationship between the level of the signal output from the pixel 10 and the level of the reference signal Vin changes (inverts) based on the signal output from the comparison unit 50 . A digital signal of the count value corresponding to the time is stored.

When the dark signal of the pixel 10 is input to the comparing section 50 , the comparing section 50 compares the dark signal with the reference signal Vin and outputs the comparison result to the storage section 55 . The storage unit 55 stores a digital signal indicating a count value corresponding to the elapsed time from the start of comparison by the comparison unit 50 to the inversion of the comparison result as a digital signal based on the dark signal. Also, when the photoelectric conversion signal of the pixel 10 is input to the comparison unit 50 , the comparison unit 50 compares the photoelectric conversion signal with the reference signal Vin and outputs the comparison result to the storage unit 55 . The storage unit 55 stores a digital signal indicating a count value corresponding to the elapsed time from the start of comparison by the comparison unit 50 to the inversion of the comparison result as a digital signal based on the photoelectric conversion signal. In this manner, the AD converter 60 can convert the dark signal, which is an analog signal, into a digital signal of a predetermined number of bits, and can convert the photoelectric conversion signal, which is an analog signal, into a digital signal of a predetermined number of bits.

The pixel signals converted into digital signals by the AD converter 60 are sequentially output to the signal processor 100 . The signal processing unit 100 receives a pixel signal converted into a digital signal (a digital signal based on a dark signal, a digital signal based on a photoelectric conversion signal). The signal processing unit 100 performs correlated double sampling for correcting the photoelectric conversion signal by subtracting the photoelectric conversion signal and the dark signal. After performing signal processing such as correlated double sampling, the signal processing unit 100 outputs the processed pixel signal to the control unit 4 .

In the present embodiment, the image sensor 3 performs a first readout control in which pixel signals are read out to one AD converter 60 and AD-converted, and a pixel signal is read out to a plurality of AD converters 60 and AD-converted. A second read control may be performed. The first read control and the second read control will be described below with reference to FIGS. 5 and 6. FIG.

5 and 6 are diagrams for explaining an example of readout control by the imaging element according to the embodiment. 5 and 6, pixel 10a in pixel block 20a, pixel 10b in pixel block 20b, pixel 10 in pixel block 20c (referred to as pixel 10c), and pixel 10 in pixel block 20d (pixel 10d). ) are shown.

When the control unit 4 instructs the read control unit 80 to perform the first read control, the read control unit 80 turns off the switches SW1a to SW1c as shown in FIG. Further, the read control unit 80 turns off the switches SW2a1 to SW2a4 of the supply units 40a to 40d shown in FIG. 4, and turns on the switches SW2b1 to SW2b4. As a result, as schematically shown in FIG. 5, the second capacitors 42a to 42d are connected between the first capacitor 41 and the ground line in each of the supply units 40a to 40d. In this case, the supply units 40a to 40d can generate the reference signals Vin1 to Vin4 of the same signal level based on the ramp signal Vramp and supply them to the AD conversion units 60a to 60d.

The read control unit 80 turns on the selectors 16 of the pixels 10a to 10d. Signals of the pixels 10a to 10d are output to the AD converters 60a to 60d via signal lines 30a to 30d, respectively. The AD converters 60a to 60d perform AD conversion of input pixel signals. The AD converter 60a compares the signal of the pixel 10a with the reference signal Vin1, and converts the signal of the pixel 10a into a digital signal.

The AD converter 60b compares the signal of the pixel 10b with the reference signal Vin2 and converts the signal of the pixel 10b into a digital signal. The AD converter 60c compares the signal of the pixel 10c with the reference signal Vin3, and converts the signal of the pixel 10c into a digital signal. The AD converter 60d compares the signal of the pixel 10d with the reference signal Vin4, and converts the signal of the pixel 10d into a digital signal. The signals converted into digital signals of the pixels 10a to 10d are stored in the storage units 55 of the AD converters 60a to 60d, respectively.

As described above, in the first readout control, the image sensor 3 reads the signals of the pixels of the pixel block 20 to the AD converter 60 provided for the pixel block 20 and AD-converts them. The pixel signals converted into digital signals by the AD converters 60 are subjected to signal processing such as correlated double sampling by the signal processor 100, and then output to the controller 4. FIG.

When the second read control is instructed by the control unit 4 and correlated multiplex sampling is performed, the read control unit 80 turns on the switches SW1a to SW1c as shown in FIG. By turning on the switches SW1a to SW1c, the signal line 30a, the signal line 30b, the signal line 30c, and the signal line 30d are electrically connected. This makes it possible to output a signal of a certain pixel to a plurality of AD converters 60 .

The readout control unit 80 controls the switches of the supply units 40a to 40d so that the reference signals Vin1 to Vin4 are shifted relative to each other. The read control unit 80 controls the switches SW2a1 to SW2a4 and the switches SW2b1 to SW2b4 shown in FIG. The number of second capacitors 42 connected between the capacitor 41 and the signal line 39 is adjusted. In the example shown in FIG. 6, the second capacitor 42a is connected between the first capacitor 41 and the signal line 39 in the supply section 40a. Also, the second capacitors 42b to 42d of the supply section 40a are connected between the first capacitor 41 and the ground line, respectively.

In the supply section 40b, the second capacitor 42a and the second capacitor 42b are connected between the first capacitor 41 and the signal line 39, respectively. The second capacitor 42c and the second capacitor 42d of the supply section 40b are connected between the first capacitor 41 and the ground line, respectively. In the supply section 40c, the second capacitors 42a to 42c are connected between the first capacitor 41 and the signal line 39, and the second capacitor 42d is connected between the first capacitor 41 and the ground line. Further, in the supply section 40d, the second capacitors 42a to 42d are all connected between the first capacitor 41 and the signal line 39. FIG. Based on the ramp signal Vramp and the signal Voffset, the supply units 40a to 40d generate reference signals Vin1 to Vin4 whose signal levels change over time from different signal levels. The supply units 40a to 40d can supply the time-shifted reference signals Vin1 to Vin4 to the AD conversion units 60a to 60d.

The readout control unit 80 turns on the selection unit 16 of the pixel 10a of the pixel block 20a among the pixel blocks 20a to 20d, for example. A signal of the pixel 10a is output to the AD converter 60a via the signal line 30a connected to the pixel 10a. The signals of the pixels 10a are also output to AD converters 60b to 60d through switches SW1a to SW1c and signal lines 30b to 30d, respectively.

The AD converters 60a to 60d compare the input signals of the pixels 10a with different reference signals Vin1 to Vin4 and convert them into digital signals. The signals of the pixels 10a can be converted into digital signals at different timings for each AD converter 60. FIG. The storage unit 55 of each of the AD conversion units 60a to 60d stores the signal of the pixel 10a converted into a digital signal. The storage unit 55 of the AD conversion unit 60a stores the signal of the pixel 10a converted into a digital signal by comparing the signal of the pixel 10a with the reference signal Vin1.

The storage unit 55 of the AD conversion unit 60b stores the signal of the pixel 10a converted into a digital signal by comparing the signal of the pixel 10a with the reference signal Vin2. The storage unit 55 of the AD conversion unit 60c stores the signal of the pixel 10a converted into a digital signal by comparing the signal of the pixel 10a with the reference signal Vin3. Further, the signal of the pixel 10a converted into a digital signal by comparing the signal of the pixel 10a and the reference signal Vin4 is stored in the storage unit 55 of the AD conversion unit 60d. The signal of the pixel 10a converted into a digital signal by each of the AD converters 60a to 60d is output to the signal processor 100. FIG. The signal processing unit 100 performs correlated multiple sampling for averaging signals of a plurality of input pixels 10a.

As described above, in the second readout control, the image sensor 3 reads out the signals of the pixels of the pixel block 20 to the plurality of AD converters 60 and AD-converts them. The pixel signals converted into digital signals by the plurality of AD conversion units 60 are subjected to signal processing such as averaging processing by the signal processing unit 100 and then output to the control unit 4 . Pixel signals are arithmetically averaged after being converted into digital signals at different timings in the plurality of AD converters 60, so that noise mixed in the pixel signals can be reduced.

A signal output from a pixel of an image sensor may be affected by noise generated in the pixel, noise generated in other circuits, and the like. For example, due to noise generated in the amplification transistor of the pixel, the signal level of the signal from the pixel, which is an analog signal, may fluctuate over time. Due to this voltage fluctuation of the pixel signal, it is conceivable that the amount of noise included in the pixel signal after AD conversion changes depending on the timing at which the AD conversion is performed in the AD conversion unit.

As described above, the image sensor 3 according to the present embodiment can perform second readout control in which pixel signals are read out to the plurality of AD converters 60 and AD-converted in the plurality of AD converters 60 at different timings. . The imaging device 3 converts the same pixel signal into a digital signal in a plurality of AD converters 60, and performs correlated multiple sampling for averaging the pixel signals converted into a plurality of digital signals. Therefore, it is possible to reduce the noise component caused by the voltage fluctuation mixed in the pixel signal. It is possible to suppress the deterioration of the signal quality of the pixels.

In the present embodiment, by controlling the switch SW1, the signals of the pixels of the pixel block 20 are transferred to the AD conversion section 60 provided for the pixel block 20 and the AD conversion section 60 provided for the other pixel blocks 20. It is possible to output to the AD conversion unit 60. For this reason, when reading signals from some pixels of the image sensor 3, when reading signals by adding signals from a plurality of pixels, etc., each AD conversion unit 60 of the image sensor 3 can be effectively used to perform correlated multiplex sampling. It can be carried out. It is not necessary to provide a large number of AD converters for each pixel block for correlated multiplex sampling, and it is possible to prevent an increase in the area of the image sensor and an increase in manufacturing cost.

FIG. 7 is a timing chart for explaining an example of second readout control by the imaging device according to the embodiment. An example of the operation of the imaging device 3 will be described below, taking as an example the case of reading the signal of the pixel 10a shown in FIGS. 5 and 6. FIG. In FIG. 7, the transistor of the pixel 10a to which a high level (eg, power supply voltage) control signal (signal SEL, signal RST, signal TX) is input is turned on, and a low level (eg, ground voltage) control signal is input. The transistor of the pixel 10a is turned off. Before time t1 shown in FIG. 7, the switches SW1a to SW1c are turned on, and the signal lines 30a to 30d are electrically connected to each other.

At time t1 shown in FIG. 7, signal RST goes high. When the signal RST becomes high level, the transistor M2 of the reset unit 14 is turned on in the pixel 10a. When the reset unit 14 is turned on, the charge of the FD 13 is reset and the voltage of the FD 13 is reset.

Also, at time t1, the signal SEL becomes high level. When the signal SEL becomes high level, the transistor M4 of the selection unit 16 of the pixel 10a is turned on. As a result, a signal based on the reset voltage of the pixel 10a, that is, a signal after resetting the charge of the FD 13 of the pixel 10a is output by the amplifier 15 and the selector 16. FIG. A signal based on the reset voltage is output as a dark signal (reset signal) to the AD converters 60a to 60d by the switches SW1a to SW1c and the signal lines 30a to 30d, respectively.

At time t2, the read control unit 80 outputs control signals to the switches SW2a1 to SW2a4 and the switches SW2b1 to SW2b4 (see FIG. 4) of the supply units 40a to 40d, and the second capacitors 42a to 42d as shown in FIG. set the connection destination. As a result, the potentials (levels) of the reference signals Vin1 to Vin4 change as shown in FIG. In this case, the amount of change in the potential of the reference signal Vin varies depending on the number of second capacitors 42 connected between the first capacitors 41 and the signal line 39 . Thus, the supply units 40a to 40d output the reference signals Vin1 to Vin4 having different initial potentials.

During the period from time t3 to time t4, the potentials of the reference signals Vin1 to Vin4 decrease over time as the potential of the signal Vramp changes. The signal levels of the reference signals Vin1 to Vin4 change over time from different signal levels. The comparators 50 of the AD converters 60a-60d compare the potential of the dark signal with the potentials of the reference signals Vin1-Vin4. The comparator 50 inverts the signal level of the output signal when the magnitude relationship between the potentials of the dark signal and the reference signal Vin changes. The storage unit 55 stores a digital signal indicating the count value when the signal level of the output signal of the comparison unit 50 is inverted. Thus, the dark signal of the pixel 10a is input to the AD converters 60a to 60d and converted into digital signals.

At time t5, the signal TX becomes high level. When the signal TX becomes high level, the transistor M1 of the transfer unit 12 is turned on in the pixel 10a. By turning on the transfer unit 12 , the charge photoelectrically converted by the photoelectric conversion unit 11 is transferred to the FD 13 . Also, at time t5, the signal SEL is at high level. Therefore, a signal (photoelectric conversion signal) based on charges generated by the photoelectric conversion unit 11 of the pixel 10 a is output by the amplification unit 15 and the selection unit 16 . A photoelectric conversion signal of the pixel 10a is output to AD converters 60a to 60d through switches SW1a to SW1c and signal lines 30a to 30d, respectively.

During the period from time t6 to time t7, the potentials of the reference signals Vin1 to Vin4 decrease over time in accordance with changes in the potential of the signal Vramp. The potentials of the reference signals Vin1 to Vin4 change over time from different initial potentials. The comparator 50 of the AD converters 60a-60d compares the potential of the photoelectric conversion signal with the potential of the reference signals Vin1-Vin4. The comparator 50 inverts the signal level of the output signal when the magnitude relationship between the potentials of the photoelectric conversion signal and the reference signal Vin changes. The storage unit 55 stores a digital signal indicating the count value when the signal level of the output signal of the comparison unit 50 is inverted.

As described above, since the initial potentials of the reference signals Vin1 to Vin4 are different, the timing at which the signal level of the output signal of each comparator 50 is inverted is different, and conversion to a digital signal is performed at different timings. It can also be said that the time correlation at the time of AD conversion differs for each AD converter 60 . The dark signal and the photoelectrically converted signal converted into digital signals by the respective AD conversion units 60 are output to the signal processing unit 100 and subjected to signal processing such as subtraction processing and averaging processing. Therefore, it is possible to reduce the noise included in the pixel signal and suppress deterioration in the quality of the pixel signal.

According to the embodiment described above, the following effects are obtained.
(1) The image sensor 3 includes a first photoelectric conversion unit that generates electric charge by photoelectric conversion, a second photoelectric conversion unit that generates electric charge by photoelectric conversion, and a first photoelectric conversion unit based on the electric charge generated by the first photoelectric conversion unit. A first signal line (signal line 30) for outputting a signal, a second signal line for outputting a second signal based on the charge generated by the second photoelectric conversion unit, and a signal output to the first signal line and a reference signal, a second comparison unit for comparing the signal output to the second signal line and the reference signal, and outputting the first signal to the first signal line a control unit (read control unit 80) that performs first control for outputting the second signal to the second signal line and second control for outputting the first signal to the first signal line and the second signal line; Prepare. In the present embodiment, by controlling the switch SW1, the readout control unit 80 can output pixel signals to the plurality of AD conversion units 60, perform AD conversion, and then perform averaging processing. Therefore, it is possible to suppress an increase in the chip area of the image sensor 3 compared to the case where a large number of AD converters are provided for each pixel block for correlated multiplex sampling.

The following modifications are also within the scope of the present invention, and it is also possible to combine one or more of the modifications with the above-described embodiments.

(Modification 1)
A signal to be output to the AD converter 60 as the reference signal Vin may be selectable from a plurality of signals. As shown in FIG. 8A, a selector 70 having a plurality of switches SW3 (switches SW3a to SW3d) may be provided. The switches SW3a to SW3d are composed of transistors. The selection unit 70 is controlled by the readout control unit 80 and selects a signal to be output as the reference signal Vin from the ramp signals Vramp1 to Vramp4. Note that the first capacitor 41 may not be arranged in FIG. 8(a). The signals Vramp1 to Vramp4 may be signals that change with relative shifts, as in the example shown in FIG. 8(b). The reference signals Vin1 to Vin4 can also be said to be signals with different phases. The read control unit 80 can change the reference signal Vin to be supplied to the AD conversion unit 60 by on/off controlling each switch of the selection unit 70 .

(Modification 2)
FIG. 9 is a diagram for explaining a configuration example of part of an imaging device according to Modification 2. As shown in FIG. The imaging element 3 is provided with switches SW4 (switches SW4a to SW4c in FIG. 9) for electrically connecting or disconnecting the FD13 of the pixel 10 and the FD13 of the other pixels 10. FIG. The switch SW4 is composed of a transistor. The switch SW4 is the connection unit 4 and connects the FDs 13 of the plurality of pixels 10 to each other.

The read control unit 80 supplies a signal to each of the switches SW4a to SW4c to control on/off of each switch. By turning on the switches SW4a to SW4c as shown in FIG. For example, the charge generated by the photoelectric conversion unit 11 of the pixel 10a can be transferred to the FD 13 of the pixel 10a and the FDs 13 of the pixels 10b to 10d. Therefore, signals based on charges generated by the photoelectric conversion unit 11 of the pixel 10a can be output to the signal lines 30a to 30d by the amplification units 15 and the selection units 16 of the pixels 10a to 10c. In the case of the second readout control, the image sensor 3 according to the present modification can output pixel signals to a plurality of AD conversion units 60 and perform AD conversion by controlling the switch SW4. .

(Modification 3)
In the embodiment described above, an example of signal readout has been described with reference to FIG. Of the pixel blocks 20a to 20d, for example, the read control unit 80 outputs the signal of the pixel 10a of the pixel block 20a to the signal line 30, and controls the signal of the pixel 10b to the pixel 10d not to be output to the signal line 30. You may do so. In the circuit diagram of FIG. 6, the readout control unit 80 turns on the selectors 16 of the pixels 10 of the pixel block 20a and turns off the selectors 16 of the pixels 10 of the pixel blocks 20b to 20d to read signals. can do

(Modification 4)
In the embodiment described above, an example in which the signal line 30 and the AD conversion unit 60 and the like are provided for each pixel block 20 has been described. However, the signal line 30 and AD converter 60 may be provided for each pixel 10 .

(Modification 5)
In the embodiment described above, an example in which the imaging element 3 is configured by laminating the first substrate 111 and the second substrate 112 has been described. However, the first substrate 111 and the second substrate 112 may not be laminated. Note that the imaging device 3 may be configured with three or more substrates, or may be configured with one substrate.

(Modification 6)
In the above-described embodiment and modified example, the example using the photodiode as the photoelectric conversion unit has been described. However, a photoelectric conversion film (organic photoelectric film) may be used as the photoelectric conversion part.

(Modification 7)
The imaging elements and imaging devices described in the above embodiments and modifications are applicable to cameras, smartphones, tablets, cameras built into PCs, vehicle-mounted cameras, cameras mounted on unmanned aerial vehicles (drones, radio-controlled machines, etc.), etc. may be

Although various embodiments and modifications have been described above, the present invention is not limited to these contents. Other aspects conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 1... Imaging device 3... Imaging element 10... Pixel 11... Photoelectric conversion part 20... Pixel block 40... Supply part 50... Comparison part 55... Storage part 60... AD conversion part 80... Read control part, 100 ... signal processing part

Claims (13)

a first photoelectric conversion unit that generates an electric charge by photoelectric conversion;
a second photoelectric conversion unit that generates an electric charge by photoelectric conversion;
a first signal line for outputting a first signal based on the charge generated by the first photoelectric conversion unit;
a second signal line for outputting a second signal based on the charge generated by the second photoelectric conversion unit;
a first comparison unit that compares the signal output to the first signal line with a reference signal;
a second comparison unit that compares the signal output to the second signal line with a reference signal;
first control for outputting the first signal to the first signal line and outputting the second signal to the second signal line; and outputting the first signal to the first signal line and the second signal line. A control unit that performs a second control that causes
An image sensor. In the imaging device according to claim 1,
An imaging device having a first connection portion for connecting or disconnecting the first signal line and the second signal line. In the imaging device according to claim 2,
In the second control, the control unit connects the first signal line and the second signal line by the first connection unit, and transmits the first signal to the first signal line and the second signal line. Image sensor for output. In the imaging device according to claim 3,
In the first control, the control unit causes the first connection unit to disconnect the first signal line and the second signal line, outputs the first signal to the first signal line, and outputs the second signal line. An imaging device for outputting a signal to the second signal line. In the imaging device according to claim 1,
a first accumulation unit that accumulates electric charge;
a second accumulation unit that accumulates electric charge;
a first transfer unit that transfers the charge generated by the first photoelectric conversion unit to the first storage unit;
a second transfer unit that transfers the charge generated by the second photoelectric conversion unit to the second storage unit;
a first output unit that outputs a signal based on the charge accumulated in the first accumulation unit;
a second output unit that outputs a signal based on the charge accumulated in the second accumulation unit;
and a second connection section for connecting or disconnecting the first accumulation section and the second accumulation section. In the imaging device according to claim 5,
The control unit controls the second connection unit to transfer the charges generated by the first photoelectric conversion unit to the first storage unit and the second storage unit, and the first output unit to transfer the charge generated by the first photoelectric conversion unit to the first storage unit. An imaging device that outputs a signal to the first signal line and outputs the first signal to the second signal line by the second output section. In the imaging device according to any one of claims 1 to 6,
The control unit outputs the first signal to the first signal line and performs third control not to output the second signal to the second signal line. In the imaging device according to any one of claims 1 to 7,
The first comparison unit compares the first reference signal and the first signal,
A said 2nd comparison part is an image pick-up element which compares a said 1st signal with a 2nd reference signal different from a 1st reference signal. In the imaging device according to claim 8,
The imaging element, wherein the second reference signal is a signal whose signal level changes over time from a signal level different from the signal level of the first reference signal. In the imaging device according to claim 8 or claim 9,
a first storage unit that stores a digital signal based on the signal output from the first comparison unit;
and a second storage unit that stores a digital signal based on the signal output from the second comparison unit. In the imaging device according to claim 10,
The first storage unit stores a first digital signal based on a signal output by comparing the first signal and the first reference signal,
The second storage unit is an imaging device that stores a second digital signal based on a signal output by comparing the first signal and the second reference signal. In the imaging device according to claim 11,
An imaging device having a processing unit that averages the first digital signal and the second digital signal. an imaging device according to any one of claims 1 to 12;
a generation unit that generates image data based on a signal output from the imaging device;
An imaging device comprising:

Images